(A) The Stormwater Quality section of the C-SWPPP shall comply with SCDHEC’s Regulations 72-300, the NPDES-CGP, and the county’s Stormwater Design Manual.
(B) All stormwater runoff generated from a site shall be adequately treated before discharge in order to ensure maximum pollutant removal is achieved to the extent where these discharges shall not cause or contribute to violations of the water quality standards. It will be presumed that a stormwater management system complies with this requirement if:
(1) For sites one acre and greater, the preferred method is to design water quality BMPs to trap 80% of total suspended solids (TSS) based on annual loadings by particle class. Other alternative methods as a default criterion include (1) designing BMPs to capture separately through BMP applications the first 1.0-inch of runoff volume from the entire drainage area of the site and discharge it over a 24-hour period, or (2) employing an anti-degradation approach to pre-development versus post development. The specific requirements for these approaches shall be described further in the Design Manual.
(a) For construction sites located within 3/4 mile of Lake Wylie, Catawba River, Broad River, a drinking water supply source, or within 500 feet of a perennial stream, as designated on the USGS map or as delineated by a professional wetlands consultant, all water quality BMPs shall be designed to achieve a sediment removal efficiency of 85% or greater for TSS.
(2) The Stormwater Administrator has discretion to require more stringent controls for water quality where the Stormwater Administrator determines the minimum standards of this section are not adequate. Areas where more stringent controls may apply include outstanding resource waters, trout waters, wetlands, steep slopes, 303(d) listed waters, TMDLs or other sensitive areas.
(C) All development and redevelopment projects and portions of redevelopment projects disturbing 1.0 acre or more of area and that will result in more than 1 cubic foot per second increase in peak runoff rates shall meet the requirements of this section even though there is not a change in land use.
(Ord. 2819, passed 6-17-19)